The first case of Ebola diagnosed in the United States was in Dallas. The biggest outbreak of West Nile virus in the country was in Dallas. And now one of the first cases of sexually transmitted Zika virus has been reported. In Dallas.

Why is thebull’s-eye on Dallas?

City leaders boast of attracting businesses and people from all over the world. Dallas is well-connected and has a booming economy, a growing population and one of the busiest airports on the planet.

It seems multiple microbes got that memo. What makes Dallas appealing to people also attracts diseases.

Even when Texas isn’t first, it’s biggest. New York City may have had the first U.S. case of West Nile, but Dallas had the biggest epidemic ever in the country. In 2012, nearly 2,000 people in the Dallas area contracted the virus, accounting for nearly half of West Nile cases in the U.S. that year.

“Our successes are grand and our tragedies are big, too,” said W.F. Strong, professor of communication and culture at the University of Texas at Brownsville and a self-proclaimed Texologist.

The roots of this grandeur go back to when Texas was coming of age, said Strong, and that mentality persists today in places such as Dallas/Fort Worth International Airport. “They built that airport as big as they could,” he said. “A larger-than-life kind of self-absorbed identity is part of the Texas mystique.”

Every day, the airport launches and lands approximately 9,000 travelers to and from countries with outbreaks of the Zika virus. With close to 300 flights each week to Mexico alone, experts are right when they say the area is well-connected.

“It’s an easy place to get to, and that’s why business is growing,” said Mayor Mike Rawlings. “That’s the good news and the bad news.”

Poverty rate

If business is on the rise in Dallas, so is poverty. The fastest-growing group in Dallas between 2000 and 2012 was people living in poverty, and the city has the highest rate of childhood poverty among cities with 1 million or more residents. Poverty is linked to the spread of infectious diseases, especially those transmitted by mosquitoes. During outbreaks of West Nile virus, researchers found poorer parts of cities to be more heavily infested with mosquitoes.

Temperatures might be on the rise, too. A study released last year by the Risky Business Project, a nonpartisan research project, predicts that the number of days when the temperature will exceed 95 degrees Fahrenheit in Texas will more than double over the next three decades.

Scientists look at factors such as temperature, poverty and ease of travel when they predict the spread of infectious diseases. In his lab at Georgia State University, Gerardo Chowell, associate professor in the school of public health, is building a mathematical model to predict how the Zika virus will spread through Latin America, the Caribbean and Dallas.

Chowell is looking to dengue fever and chikungunya for clues about where the Zika virus will travel next. All three infections are spread by the Aedes aegypti mosquito, which can be found in North Texas. Chowell predicts small local outbreaks of the Zika virus in Texas and Florida based on what’s been seen with dengue fever.

In 2005 and 2013, dengue caused outbreaks in Texas among people who hadn’t left the country.

“Zika is a similar situation to dengue. We’ll probably see small outbreaks of Zika in Texas,” said Chowell. “The populations in Dallas are from everywhere, you have the mosquito and you’re well-connected to many parts of the world.”

News that a person in Dallas was infected with the Zika virus through sex makes Chowell’s job harder. Until the Dallas case was reported, there was only one other known case of Zika being transmitted through sex. Most experts, including Chowell, still believe that the main culprit in the current outbreak is the mosquito and not unprotected sex.

But why was this sexually transmitted case discovered in Dallas where there are a handful of Zika cases instead of Brazil or Colombia where there are thousands? The question isn’t “Why Dallas?” The answer is because Dallas, said Dallas County Judge Clay Jenkins.

He argues that if Zika was spreading through sex in smaller towns with fewer resources, the link to sex may never have been detected.

“It would be very rare that in a rural setting the local health department would have had the capability to do the epidemiological detective work to find the mode of transmission,” Jenkins said.

Long history

Zika isn’t the first mosquito-borne infection to make its mark on Texas. The University of Texas at Brownsville sits on what used to be Fort Brown, one of the oldest Army forts on the border and the launching point for the Mexican-American war.

Strong said he’s reminded of the state’s long, infectious past every time he’s on the campus. “When this was a fort in the 1800s, this was the sickest fort in the U.S. Army,” he said. Back then, hundreds of soldiers died from malaria and Yellow Fever. An astute physician, Dr. William Gorgas, figured out that mosquitoes were spreading these diseases.

Gorgas was so successful at protecting the health of Texas troops by draining standing water that he was sent to the Panama Canal to implement the same public health measures.

“He turned out to be the savior of the Panama Canal when they couldn’t complete it because the workers were too sick,” said Strong. A building on the university campus and a world-famous — at least among doctors — infectious disease program in Peru are named for Gorgas.

Innovation against mosquitoes and the diseases they spread continues to take place in the state. At Tarrant County Health, public information officer Kelly Hanes said the arrival of these diseases might be a good thing. It keeps the area at the forefront of the discussion on how to manage public health emergencies. And for Hanes and his colleagues, they offer job security.

“Think about it. If you lived somewhere where novel diseases weren’t happening, you might be the first budget item that the city or the state decides to cut. ‘Oh we don’t need 20 epidemiologists, we just need 12.’ And then you’re gone. But here, everybody is like ‘We need more epidemiologists. We need more!’ ” he said.

Dr. Seema Yasmin, a physician and former CDC epidemiologist, is a professor at the University of Texas at Dallas.